Determinat of Some Carotenoids

Technical Support and Questions

Hi. I saw protocol for measurement anthocyanins (only V1.0). 510-540 nm have absorption maxima most natural anthocyanins. The absorption spectra of carotenoids have an intense band at 400-500 nm. I know that Carotenoids (zeaxanthin (480 nm), violaxanthin (490)) provide non-photochemical quenching etc.
How do you think. Is it possible to create a protocol for their determination? Thanks!

Maybe this questions is incorrect because i see that LEDs have a clearly defined value range 530, 650, 605, 420, 940, 850, 730, 880. Topic is closed. Sorry.

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Greg Austic

Aug 2016

I think it's a good question. So we tried to estimate anthocyanins (https://photosynq.org/projects/fall-tree-leaf-anthocyanin-content unfortunately Ryan didn't post his results, but we should do that) using the Beta and could get a reasonable correlation but only at very high concentrations. The interest was to correlate anthocyanins with stress, but the change during stress is pretty small and hard to see with lots of noise. It's possible that, due to the much improved signal to noise, we'll have a better change to see changes in the v1.0 but so far we just don't know. But by default in every measurement we are measuring absorbance in every LED that we can (420, 535, 605, 650, 730, 850, 880, 940)... my hope is that we can build correlations from that data... I have a feeling (just a guess here) that we're going to see correlations to stress fairly quickly, but we won't know the mechanism without some detailed study (taking destructive leaf samples and measuring chemical components).

This would be a great thing to work on with the v1.0!

In science articles i found Ap (index adaptation to stress) = 1 – (1 + Rfd735)/(1 + Rfd690), where Fo and Fm measured on 735nm and 690nm. Our device can work in these ranges ? It is possible to create a protocol for measuring in this range, maybe in future.

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Greg Austic

Aug 2016

735 we have, but we don't have 690. Closest we have is 650. The actual wavelength of all our LEDs are a normal distribution around whatever value they state, so the 650 may touch into the 690 region a little bit... but also our 2 detectors (IR and visible) cutoff right at 700 so signal will be weak there for either.

So at first glance I'd say possible to investigate but might be hard to get that exact data.

What kind of Rfd i have from MultispeQ? Rdf730 (Fm730, F0730, Fs730)?

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Greg Austic

Aug 2016

Not sure if I fully understand the question, but there is a 730nm far red LED which is exciting PSI and draining the plastiquinone pool but I don't think that's what you mean. The measurement light is 605nm. Can you rephrase?

Ok. Now I know, that 605 - for fluorescence measurement, 650 and 940 - chlorophylls measurement, 730 - exciting PSI and draining the plastoquinone, 535 - ECS measurement. I am sorry, that i have many questions. Thanks.

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Greg Austic

Aug 2016

Yep - you got it! And if you haven't seen it, we're documenting how to build protocols with the new device here:

https://github.com/Photosynq/PhotosynQ-Firmware/wiki

There's also a nice schematic there as well with the LEDs and their primary wavelengths, as well as the internal structure of the device.

https://www.dropbox.com/s/cipk8vl1s71oozi/drawing%20of%20hardware.pdf?dl=0

While we wait for manufacturing, we're trying to improve our documentation and make interacting with the platform easier, hopefully these types of things help.